Preview when form input changes

On one of the pages in my Phoenix project, I have a form. When someone changes this form, I want to show an updated preview to let the user see what this change will do.

I am, however, confused by two things:

  1. How can I properly pass the form data through a Phoenix channel, and manipulate it just like a normal Changeset server-side?
  2. How can I render a server-side html response and send it back over the channel so JS can inject it?